This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C xc2xa7119 from an application entitled AWG WDM Provided With Alignment Waveguides And Apparatus For Aligning The Same earlier filed in the Korean Industrial Property Office on Jun. 21, 1999, and there duly assigned Ser. No. 1999 -23273 by that Office.
1. Field of the Invention
The present invention relates to an arrayed waveguide grating (AWG) wavelength division multiplexer (WDM) provided with alignment waveguides, and an apparatus for aligning the arrayed waveguide grating wavelength division multiplexer.
2. Description of the Related Art
Generally, a waveguide type optical device should be bonded to optical fibers in a state aligned with those optical fibers so that it is practically usable for a transmission network. For the bonding and alignment of the optical device, a light is first incident to an input optical fiber array. Using the incident light, the input optical fiber array is then aligned with an input waveguide array of the optical device. Thereafter, an output optical fiber array is aligned with an output waveguide array of the optical device so as to allow the light to be guided to two ports positioned at respective outermost positions on the end of the output optical fiber array. A detection for the intensity of the light guided to the ports is then carried out. Based on the result of the detection, the relative position of each optical fiber array and the optical device is finely adjusted to find a position where alight is guided with a maximum intensity. At the found position, the associated optical fiber array is then bonded to the optical device
FIG. 1a illustrates a conventional wavelength division multiplexer. FIG. 1b is a cross-sectional view illustrating an optical fiber block aligned with the wavelength division multiplexer of FIG. 1a. 
The wavelength division multiplexer shown in FIG. 1a includes an input waveguide array 101, a first star coupler 102, an arrayed waveguide grating (AWG) 103, a second star coupler 104, and an output waveguide array 105. An optical fiber block shown in FIG. 1b is bonded to each of the input and output waveguide arrays 101 and 105 in an aligned state.
Examples of waveguide arrays utilizing star couplers are discussed in: U.S. Pat. No. 5,002,350 entitled Optical Multiplexer/Demultiplexer to Corrado Dragone; U.S. Pat. No. 6,058,233 entitled Waveguide Array With Improved Efficiency For Wavelength Routers And Star Couplers In Integrated Optics to Corrado Dragone; and U.S. Pat. No. 6,067,388 entitled Method Of Making An Integrated Optical Component And An Integrated Optical Star Coupler Made In Accordance With Said Method to Norbert Fabricius et al., each being incorporated by reference herein.
Where an optical device, such as the above mentioned wavelength division multiplexer, is to be bonded to an optical fiber block in an aligned state, it is necessary to spatially accurately align the optical device and optical fiber block while taking into consideration the wavelength characteristics of the optical device in order to find an optimum bonding position. The wavelength characteristics, however, of the optical device may vary during the manufacture of that optical device, and should be known prior to the alignment process of the optical device. Furthermore, for the alignment of the optical device, it is necessary to use a number of complex devices, for example, a number of light sources.
For a wavelength division multiplexer as mentioned above, it is also important to monitor an optical signal, transmitted through the WDM, at an optical position of the wavelength division multiplexer in real time. In a conventional monitoring method, signal information output from each port of the wavelength division multiplexer is read to detect the wavelength of the optical signal. In accordance with this method, however, it is necessary to directly input, to a detector, the optical signal output from the end of a transmission line or the output end of the wavelength division multiplexer. For this reason, it is impossible to achieve the wavelength detection during the transmission of the optical signal.
Therefore, an object of the invention is to provide an improved arrayed waveguide grating wavelength division multiplexer.
Another object of the invention is to provide an arrayed waveguide grating wavelength division multiplexer provided with alignment waveguides capable of outputting optical signals distributed from an input optical signal, as they are.
Yet another object of the invention is to provide an apparatus for aligning the arrayed waveguide grating wavelength division multiplexer with optical fiber blocks.
Also, another object of the invention is to provide an apparatus for aligning the arrayed waveguide grating wavelength division multiplexer with optical fiber blocks utilizing optical signals distributed from an input optical signal, as is, via alignment waveguides.
A further object of the invention is to provide a method for aligning the arrayed waveguide grating wavelength division multiplexer with optical fiber blocks.
Further yet, an object of the invention is to provide a method for aligning the arrayed waveguide grating wavelength division multiplexer with optical fiber blocks utilizing optical signals distributed from an input optical signal, as is, via alignment waveguides.
In accordance with one aspect, an arrayed waveguide grating wavelength division multiplexer comprising: a plurality of input waveguides; a first star coupler for distributing optical signals received from the input waveguides; an arrayed waveguide grating having a plurality of waveguides with different lengths and serving to guide a part of the distributed optical signals via the waveguides while allowing the guided optical signals to have different phases; a second star coupler for diffracting the optical signals having different phases, thereby causing the diffracted optical signals to interfere with one another; a plurality of output waveguides connected to the second star coupler and adapted to output the interfering optical signals; and alignment optical fibers connected to an output terminal of the first star coupler and arranged outside the arrayed waveguide array and the output wave guides, the alignment optical fibers serving to guide the remaining optical signals, output from the first star coupler, irrespective of the wavelengths of the optical signals.
In accordance with another aspect, the present invention provides an apparatus for aligning, with optical fibers, an arrayed waveguide grating wavelength division multiplexer adapted to conduct a distribution of input lights and a separation and combination of the wavelengths of the distributed lights, and to output the resultant lights, comprising: a light source; a first optical fiber block mounted with a plurality of optical fibers and adapted to guide a light emitted from the light source via the optical fibers; an arrayed waveguide grating wavelength division multiplexer adapted to distribute lights respectively received from the optical fibers of the first optical fiber block, the wavelength division multiplexer being provided with a plurality of alignment waveguides serving to output a part of the distributed lights as they are, and a plurality of functional waveguides serving to output the remaining distributed lights in a separated or combined state; a second optical fiber block mounted with a plurality of alignment optical fibers respectively aligned with the alignment waveguides of the wavelength division multiplexer, and a plurality of functional optical fibers respectively aligned with the functional waveguides of the wavelength division multiplexer; a measuring unit for measuring respective intensities of the lights output from the alignment optical fibers of the second optical fiber block; and a control unit for adjusting respective positions of the first and second optical fiber blocks and the wavelength division multiplexer at which the measured intensities of the lights are maximized.